Conventionally, improving fuel efficiency of a vehicle has been carried out by reducing the rolling resistance of a tire and suppressing generation of heat. Among tire members, a tread having a high occupancy in a tire is required to have excellent low heat build-up.
In order to solve the problems, silica is recently used as a reinforcing filler for the tread of the tire.
However, since the affinity of silica with rubber is lower than that of carbon black, a reinforcing effect is low.
In order to achieve the same reinforcing property as that of carbon black, the reinforcing property is tried to be increased by improving the dispersibility of silica or chemically bonding rubber to silica. Specifically, addition of a silane coupling agent and use of terminal-modified SBR for silica have been investigated.
As a method of satisfying the low heat build-up, a method in which the amount of silica to be mixed as a reinforcing filler is decreased and a method using a filler having low reinforcing property are known. However, the methods have problems of largely decreasing wear resistance performance and grip performance.
In order to solve the problems, for example, Patent Document 1 proposes “a rubber composition for tire treads including (A) a diene rubber containing a vinyl group, (B) silica having a nitrogen adsorption specific surface area of from 30 to 500 m2/g and/or carbon black having a nitrogen adsorption specific surface area of from 22 to 250 m2/g, and (C) unvulcanized composite microparticles containing a compound having two or more mercapto groups in the molecule” (claim 1).